1. Field of the Invention
The present invention relates to a method and a device for recovering a frame alignment word in a digital transmission signal wherein a synchronization information is constitued of a binary alignment word having N bits that are distributed in the frame of the digital signal.
2. Description of the Prior Art
Such a synchronization method has already been used in radio channel transmission having a bit-rate lying between 2 and 280 Mbit/s. Methods then implemented for recovering frame alignment are that much faster the higher the bit-rate. This is why the frame alignment recovery times remain within acceptable limits.
In telephone systems where digitalization of the subscriber line is currently under development, it is planned to use a synchronization pattern of the distributed type, as broached earlier. However, in this case, the bit-rate to be taken into consideration for transmission is a basic value equal to the information bit-rate between the subscriber telephone installation and a telephone exchange. From a practical viewpoint, the value of the bit-rate chosen is 160 kbit/s corresponding to a useful information rate of 144 kbit/s. For these digital bit-rate values, the usual frame alignment recovery methods are no longer suitable since they imply high frame recovery times.